Cross-sectional functionally graded propellants and method of manufacture

Abstract

Methods of making cross sectional, functionally-graded munitions propellants exhibiting various distributions of particle concentrations and burn rate, including having a fast burning core and slower burning outer layer(s). Unlike prior art methods of preparing such munitions, propellants prepared according to our inventive method(s) may be performed substantially as a single extrusion step or as a few processing steps, without requiring the time, expense and / or difficulties that characterized familiar, laminating methods and methods which use multiple extruders. Our inventive method advantageously employs a demixing phenomenon that, prior to our inventive application and teaching, has been considered quite undesirable in the preparation of propellants where uniformity and well-mixedness have been propellant attributes widely sought after.

Description

CROSS REFERENCE TO RELATED APPLICATION[0001]This application claims the benefit under 35 USC 119(e) of U.S. Provisional Patent Application No. 60 / 521,055 filed Feb. 12, 2004, the entire file wrapper contents of which provisional application are herein incorporated by reference as though set forth at length.FEDERAL RESEARCH STATEMENT[0002]The invention described herein may be made, used, or licensed by or for the United States Government for government purposes without payment of any royalties thereon or therefore.BACKGROUND OF THE INVENTION[0003]1. Field of the Invention[0004]This invention relates generally to the field of munitions propellants and in particular it relates to propellants that are functionally-graded over their cross-sectional areas and corresponding method of manufacture in which individual grains of the munitions propellant have particle concentration, and hence burn rate distributions, including a fast burning core and slower burning outer region(s).[0005]2. Desc...

AI Technical Summary

Benefits of technology

[0012]We have developed a method of preparing munitions propellants which are functionally-graded over their cross-sectional areas, including having a fast burning core and slower burning outer layer(s). Unlike prior art methods of preparing such munitions propellants, our inventive method may be performed substantially as a single or relatively few processing steps, without requiring the time, expense and / or difficulties that characterized familiar, laminating methods or the use of multiple processing machinery.

[0014]According to a first embodiment of our invention, a single, bulk formulation of munitions propellant is driven under pressure through die and / or pipes of sufficient length such that propellant components are stratified by concentration producing a desirable, cross-sectional concentration gradient in the extruded propellant. The resulting cross-sectional, functionally graded propellant advantageously exhibits a faster burning core and a slower burning outer layer(s).

[0017]Additionally, our inventive method may advantageously result in a functionally graded propellant having a binder / plasticizer outer boundary that is less sensitive to initiation, thereby facilitating the further development of highly desirable, Insensitive Munitions (IM).

[0018]Lastly, our inventive method provides for the reuse of manufacturing “scrap”, for thermoplastic binders, such that it may be returned to the bulk formulation and turned into finished product, rather than discarded which adds cost and raises environmental concerns, as would be the case with existing preparative method(s).

Problems solved by technology

Our inventive method employs the demixing phenomenon that, prior to our inventive application and teaching, has been quite undesirable in the preparation of propellants, where uniformity and well-mixed have been propellant attributes widely sought after.

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